The present invention relates to a novel positive-working resist composition or, more particularly, to a novel chemical-sensitization positive-working photoresist composition with high sensitivity having high transparency to the ArF excimer laser beams and capable of giving a positively patterned resist layer having excellently orthogonal cross sectional profile and high resistance against dry etching as well as high adhesion to the substrate surface.
It is a remarkable trend in recent years that the photolithographic patterning works in the manufacture of various kinds of electronic devices such as semiconductor devices and liquid crystal display panels are conducted increasingly by using a chemical-sensitization photoresist composition in place of conventional photoresist composition of other types. A chemical-sensitization photoresist composition contains a radiation-sensitive acid-generating compound from which an acid is released in the photoresist layer by the pattern-wise exposure to actinic rays while the thus generated acid catalytically acts on the film-forming resinous ingredient of the composition which causes, by the interaction with an acid, a change of the solubility in an aqueous alkaline developer solution. Accordingly, chemical-sensitization photoresist compositions are advantageous in respects of their high photosensitivity and high pattern resolution even with a relatively low content of the acid-generating agent.
Chemical-sensitization photoresist compositions are classified into positive-working and negative-working compositions depending on the types of the film-forming resinous ingredients which cause an increase and decrease, respectively, of the solubility in an aqueous alkaline developer solution by interacting with the acid generated from the acid-generating agent when the resist layer is pattern-wise exposed to actinic rays.
The most important resinous compound suitable as the above mentioned film-forming resinous ingredient in the chemical-sensitization photoresist compositions is a polyhydroxystyrene resin optionally substituted for a part of the hydroxyl groups therein by acid-dissociable solubility-reducing groups in view of the high transparency of the resin to the KrF excimer laser beams of 248 nm wavelength used as the actinic rays for pattern-wise exposure.
Along with the trend in the modern semiconductor devices toward finer and finer patterning of the resist layer, the photolithographic process by using ArF excimer laser beams of 193 nm wavelength is now on the starting line to replace the process by using KrF excimer laser beams of 248 nm wavelength. Since resinous ingredients having a benzene ring in the molecular structure, such as the above mentioned polyhydroxystyrene, can hardly be used in the photolithographic patterning process by using the ArF excimer laser beams due to the relatively low transparency of the resin to the light of such a short wavelength, proposals have been made for resins usable in the ArF excimer laser beam process, of which acrylic resins such as polymethyl methacrylate are now highlighted.
As such an acrylic resin capable of satisfying both of the requirements for the UV transparency and dry etching resistance, proposals are made for polymers of an acrylic acid ester having an alicyclic hydrocarbon group introduced into the ester-forming part including, for example, polymeric resins of a (meth)acrylic acid ester having an adamantane structure in the ester-forming group disclosed in Japanese Patent Kokai 4-39665 and polymeric resins of a (meth)acrylic acid ester having a terpenoid ring structure, such as menthol residue, in the ester-forming group disclosed in Japanese Patent Kokai 8-82925.
The above mentioned resins of a (meth)acrylic acid ester having an adamantane structure, however, are not practicable because, in addition to the expensiveness, the photosensitivity of the photoresist compositions formulated with such a resin is not high enough and the resist composition cannot give a patterned resist layer having an excellently orthogonal cross sectional profile and the photoresist compositions formulated with a resin of a (meth)acrylic acid ester having a terpenoid, e.g., menthol, structure cannot give a resist layer having high resistance against dry etching.
While the process using the ArF excimer laser beams has been developed with an object to accomplish good pattern resolution for ultrafine patterning with a line width of 0.2 .mu.m or even smaller, an important requirement in such ultrafine patterning is high adhesion between the substrate surface and the patterned resist layer formed thereon since otherwise troubles are sometimes caused due to failure of patterning.